crash on reading ICS calendar when no timezone is given

[throni3git]

when tested with a fresh calendar with some whole-day events, Chronos crashed as it did not receive timezone info. indeed the temporarily created tmp/<name>.ics file is not having a timezone info at the beginning.

• calendar created with Nextcloud
• some whole-day events inserted
• run Chronos with a config including this as as source calendar

how to handle this? can this happen with an empty CalDAV calendar as well?

[throni3git]

traceback:

[2026-02-22 20:41:51+0100][chronos.app_factory                 app_factory.py: 120] CRITICAL:  Cron excecution failed. Reason expected str, bytes or os.PathLike object, not NoneType
Traceback (most recent call last):
  File "/mnt/daaaten/Arbeit/github/ILSC-Chronos/src/chronos/app_factory.py", line 110, in single_run
    self.read_calendars()
  File "/mnt/daaaten/Arbeit/github/ILSC-Chronos/src/chronos/app_factory.py", line 66, in read_calendars
    calendar.read()
  File "/mnt/daaaten/Arbeit/github/ILSC-Chronos/src/chronos/calendar_handler.py", line 90, in read
    self.read_ics_from_url()
  File "/mnt/daaaten/Arbeit/github/ILSC-Chronos/src/chronos/calendar_handler.py", line 124, in read_ics_from_url
    self.cal_timezone_info = zoneinfo.ZoneInfo(timezone_id)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/zoneinfo/_tzpath.py", line 67, in find_tzfile
    _validate_tzfile_path(key)
  File "/usr/lib64/python3.11/zoneinfo/_tzpath.py", line 80, in _validate_tzfile_path
    if os.path.isabs(path):
       ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/posixpath.py", line 62, in isabs
    s = os.fspath(s)
        ^^^^^^^^^^^^
TypeError: expected str, bytes or os.PathLike object, not NoneType